Titanium-45 (45Ti) is a radionuclide with desirable physical characteristics for use in positron emission tomography (PET) imaging including a moderate half-life (3.08 h), decay by positron emission (85%), and low mean positron energy of 0.439 MeV. Despite these promising characteristics, the radiochemistry for 45Ti including the development of suitable bifunctional chelators is relatively unexplored compared to that of other radiometals. This work investigated three hydroxypyridinone compounds, viz., 3,2,3-(LI-1,2-HOPO) or C8-HOPO, 3,3,3-(LI-1,2-HOPO) or C9-HOPO, 3,4,3-(LI-1,2-HOPO) or C10-HOPO as potential chelators for 45Ti. Radiolabeling optimization, stability, and biodistribution results demonstrated C9-HOPO to be a promising chelator for 45Ti. In vivo evaluation of the [45Ti]Ti-C9-HOPO complex indicated rapid clearance with no signs of decomplexation.
